Methods and Systems for Measuring a Characteristic of a Substrate or Preparing a Substrate for Analysis

ABSTRACT

Methods and systems for measuring a characteristic of a substrate or preparing a substrate for analysis are provided. One method for measuring a characteristic of a substrate includes removing a portion of a feature on the substrate using an electron beam to expose a cross-sectional profile of a remaining portion of the feature. The feature may be a photoresist feature. The method also includes measuring a characteristic of the cross-sectional profile. A method for preparing a substrate for analysis includes removing a portion of a material on the substrate proximate to a defect using chemical etching in combination with an electron beam. The defect may be a subsurface defect or a partially subsurface defect. Another method for preparing a substrate for analysis includes removing a portion of a material on a substrate proximate to a defect using chemical etching in combination with an electron beam and a light beam.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to methods and systems formeasuring a characteristic of a substrate or preparing a substrate foranalysis. Certain embodiments relate to methods and systems formeasuring a characteristic of a substrate or preparing a substrate foranalysis that include removing a portion of a material on a substrate.

2. Description of the Related Art

The following descriptions and examples are not admitted to be prior artby virtue of their inclusion within this section.

Fabricating semiconductor devices such as logic and memory devicestypically includes processing a substrate such as a semiconductor waferusing a number of semiconductor fabrication processes to form variousfeatures and multiple levels of the semiconductor devices. For example,lithography is a semiconductor fabrication process that involvestransferring a pattern from a reticle to a resist arranged on asemiconductor wafer. Additional examples of semiconductor fabricationprocesses include, but are not limited to, chemical-mechanicalpolishing, etch, deposition, and ion implantation. Multiplesemiconductor devices may be fabricated in an arrangement on asemiconductor wafer and then separated into individual semiconductordevices.

Throughout the fabrication process, parameters of features formed on thewafer are measured for process monitoring and control purposes. Forexample, three dimensional metrology of the profile of features on amonitor wafer is often performed at various times during the process. Inparticular, the three-dimensional profile of photoresist features isoften measured after a lithography step to determine if the featureshave parameters that are within the specifications (specs) set for them.If the parameters of the features are within spec, then the lithographystep may be performed on product wafers. On the other hand, if theparameters of the features are not within spec, then one or moreparameters of the lithography step may be altered. Another monitor wafermay then be exposed in the lithography process, and the measurementsdescribed above may be performed until the parameters of the featuresare within spec.

The term “monitor wafer” is generally defined as a wafer upon which asemiconductor product will not be formed. Instead, monitor wafers areonly used to monitor the parameters of one process tool and, therefore,are generally only processed in that one tool. After use, monitor wafersmay be recycled or scrapped depending on the process that they were runthrough. Monitor wafers are particularly used as process monitors when ametrology or inspection process will damage the wafer. In this manner,monitor wafers, instead of product wafers, will be destroyed therebyreducing the costs of metrology or inspection. However, using monitorwafers to monitor and control processes can be relatively expensive ifthe monitor wafers are so damaged by metrology or inspection that theycannot be reused. In addition, since there may be significantdifferences between monitor wafers and product wafers (e.g., usuallyfewer processes are performed on the monitor wafers than the productwafers which can produce significant differences in the wafers), usingmonitor wafers may not provide results that are as accurate asmeasurements performed on a product wafer.

As a result, there are advantages to performing metrology and inspectionon product wafers. However, as mentioned above, many metrology andinspection processes damage wafers. For example, wafers on whichphotoresist features are formed are often cleaved (i.e., fractured)through the photoresist features such that cross-sectional profiles ofthe features on the cleaved samples can be viewed. Since the wafers arefractured, this destructive metrology technique results in scrappedwafers. Another metrology technique involves photoresist featurecross-sectioning uses ion beams. For 193 nm photoresist features andsmaller lines, the photoresist features are exposed to a tungsten orplatinum deposition to reduce ion beam induced damage. The depositedmetal top layer generates stresses on 193 nm photoresist lines therebyresulting in photoresist compression and deformation. This damage isdue, at least in part, to the incomplete conformal coating of thesubstrate during the deposition process, which produces voids betweenadjacent photoresist features. The resulting cross-section thus losesstructural integrity, and sometimes to such a degree that the resultsare not a viable indicator of the characteristics (e.g., criticaldimension) of the features. In addition, in such metrology techniques,the use of gallium or other metallic liquid ion sources produces metalcontamination in the front end of the line (FEOL) portion ofsemiconductor device fabrication. There are, therefore, severaldisadvantages to the currently used three-dimensional metrologytechniques including destroyed and therefore scrapped wafers, metalcontamination, and/or deformed photoresist features.

As the dimensions of advanced semiconductor devices continue to shrink,the presence of defects in the semiconductor devices increasingly limitsthe successful fabrication, or yield, of the semiconductor devices. Forexample, a scratch formed on a wafer during chemical-mechanicalpolishing may cause an open circuit or a short circuit in, or completefailure of, one or more semiconductor devices formed in subsequentprocessing. Because fabrication of a semiconductor device includes manycomplex process steps, the adverse effects of defects on total yield mayincrease exponentially if a defect formed on a wafer in onemanufacturing process step causes additional defects to be formed on thewafer in subsequent manufacturing process steps.

Accordingly, defect detection or “inspection” of semiconductor wafers isand will continue to be of significant importance in semiconductordevelopment and manufacturing. In addition, the review and analysis ofdefects is of significant importance such that the cause of defects maybe determined and hopefully corrected. The ability to remove device filmlayers (“de-layer”) at select locations in a controllable fashion iscritical for defect review and analysis during the device fabricationprocess. For example, removing a device film layer may allow a betterview of a defect, particularly a subsurface or partially subsurfacedefect. In addition, removing a device film layer may enable analysis ofthe defect composition to be performed with less interference from thesurrounding film layer.

Current techniques for de-layering of a substrate utilize ion beametching, laser ablative etching, or mechanical abrasion using amicro-tip. Focused ion beam etching utilizes gallium ions to stimulateetching. Laser ablative techniques utilize lasers to heat the surface ofthe substrate to cause chemical and thermal reactions that remove thefilms. The mechanical abrasion technique uses micro-tips to remove thefilms around the defect.

Of the current techniques, ion beam etching is the most mature techniqueused to de-layer devices. However, when using an ion beam to stimulateetching, gallium ions from a source are implanted into the films, whichcan lead to changes in the optical, electrical, and mechanicalproperties of the etched features and the surrounding areas. Thepresence of gallium ions on the device can limit further processing ofthe device and the wafer in the fab, which would result in scrapping theentire wafer. In addition, during focused ion beam etching, the etchedmaterial may be deposited in the surrounding areas on the wafer. Theother techniques used for de-layering of a substrate also have severaldisadvantages. For example, the laser ablative technique has low etchselectivity. In addition, the mechanical abrasion method has limitedapplications to certain large defects and films.

Accordingly, it would be advantageous to develop methods and systems forthree-dimensional metrology of features on a substrate and forde-layering a material on a substrate, which do not destroy,contaminate, or deform the substrate or the features.

SUMMARY OF THE INVENTION

The following description of various embodiments of methods and systemsfor measuring a characteristic of a substrate or preparing a substratefor analysis is not to be construed in any way as limiting the subjectmatter of the appended claims.

An embodiment of the invention relates to a method for measuring acharacteristic of a substrate. In one embodiment, the substrate mayinclude a product wafer. The method includes removing a portion of afeature on the substrate using an electron beam to expose across-sectional profile of a remaining portion of the feature. Removingthe portion of the feature does not substantially deform the remainingportion of the feature. In addition, the portion of the feature that isremoved is substantially confined to an area of the feature illuminatedby the electron beam. In one embodiment, the feature may include aphotoresist feature.

The method also includes measuring a characteristic of thecross-sectional profile of the remaining portion of the feature. Thecharacteristic of the cross-sectional profile includes athree-dimensional characteristic of the feature. In one embodiment,measuring the characteristic may be performed using the electron beam.In such an embodiment, the method may also include tilting the substraterelative to the electron beam between removing the portion of thefeature and measuring the characteristic. In a different embodiment,measuring the characteristic may be performed using a different electronbeam. The different electron beam may be arranged at a predeterminedtilt position with respect to the substrate. Each of the embodiments ofthe method described above may include any other step(s) describedherein.

Another embodiment relates to a system configured to measure acharacteristic of a substrate. In one embodiment, the substrate includesa product wafer. The system includes an electron delivery subsystemconfigured to deliver one or more electron beams to the substrate. Theone or more electron beams can remove a portion of a feature on thesubstrate to expose a cross-sectional profile of a remaining portion ofthe feature. In one embodiment, the feature includes a photoresistfeature. Removal of the portion of the feature does not substantiallydeform the remaining portion of the feature. The portion of the featurethat is removed is substantially confined to an area of the featureilluminated by the one or more electron beams.

The one or more electron beams can also measure a characteristic of thecross-sectional profile of the remaining portion of the feature. Thecharacteristic of the cross-sectional profile includes athree-dimensional characteristic of the feature. In one embodiment, thesystem may be configured to tilt the substrate relative to the one ormore electron beams between removal of the portion of the feature andmeasurement of the characteristic. In another embodiment, removal of theportion of the feature is performed using a first of the one or moreelectron beams. Measurement of the characteristic is performed using asecond of the one or more electron beams. The second electron beam maybe arranged at a predetermined tilt position with respect to thesubstrate. Each of the embodiments of the system described above may befurther configured as described herein.

An additional embodiment relates to a method for preparing a substratefor analysis. The substrate may include a product wafer. The methodincludes removing a portion of a material on the substrate proximate toa defect using chemical etching in combination with an electron beam.The defect may include a subsurface defect or a partially subsurfacedefect. The portion of the material that is removed may have an areathat is equal to or less than about 10 μm by about 10 μm. Chemicaletching may include exposing the substrate to an etch chemistry. Theetch chemistry may include a fluorine-based chemistry, a chlorine-basedchemistry, a bromine-based chemistry, or an oxygen-based chemistry. Insome embodiments, the method may also include removing a portion of anadditional material on the substrate proximate to the defect using thechemical etching in combination with the electron beam. The additionalmaterial is different than the material and is formed under thematerial.

In one embodiment, the method may include analyzing the defect todetermine a characteristic of the defect. For example, the method mayinclude analyzing the defect using the electron beam to determine acharacteristic of the defect. In another embodiment, the method mayinclude analyzing the defect using an x-ray analysis system to determinea characteristic of the defect. The characteristic of the defect mayinclude a composition of the defect. Each of the embodiments of themethod described above may include any other step(s) described herein.

A further embodiment relates to a system configured to prepare asubstrate for analysis. In one embodiment, the substrate includes aproduct wafer. The system includes a chemical delivery subsystemconfigured to deliver one or more chemicals to a substrate. The systemalso includes an electron delivery subsystem configured to deliver anelectron beam to the substrate. The one or more chemicals in combinationwith the electron beam remove a portion of a material on the substrateproximate to a defect. The defect may include a subsurface defect or apartially subsurface defect. The portion of the material that is removedmay have an area that is equal to or less than about 10 μm by about 10μm.

In one embodiment, the one or more chemicals may include afluorine-based chemistry, a chlorine-based chemistry, a bromine-basedchemistry, or an oxygen-based chemistry. The one or more chemicals incombination with the electron beam may also remove a portion of anadditional material on the substrate proximate to the defect. Theadditional material is different than the material and is formed underthe material.

In some embodiments, the system may also include an analysis subsystemconfigured to measure a characteristic of the defect. In one embodiment,the electron delivery subsystem may be configured to measure acharacteristic of the defect using the electron beam. In this manner,the electron delivery subsystem may also function as an analysissubsystem. In another embodiment, the analysis subsystem may include anx-ray analysis system. In some embodiments, the characteristic of thedefect may include a composition. Each of the embodiments of the systemdescribed above may be further configured as described herein.

Yet another embodiment relates to a different method for preparing asubstrate for analysis. This method includes removing a portion of amaterial on the substrate proximate to a defect using chemical etchingin combination with an electron beam and a light beam. The electron beamis delivered to the substrate coaxially with the light beam. Chemicaletching includes exposing the substrate to an etch chemistry. In oneembodiment, the etch chemistry may include a fluorine-based chemistry, achlorine-based chemistry, a bromine-based chemistry, or an oxygen-basedchemistry. Removing the portion of the material includes heating thematerial with the light beam. In addition, removing the portion of thematerial includes heating a horizontal surface of the material and notsubstantially heating a vertical surface of the material. The portion ofthe material that is removed may have an area that is equal to or lessthan about 10 μm by about 10 μm.

In one embodiment, the method includes generating the light beam with alaser. In some embodiments, the method may also include removing aportion of an additional material on the substrate proximate to thedefect using the chemical etching in combination with the electron beamand the light beam. The additional material is different than thematerial and is formed under the material. Removing the portion of thematerial and removing the portion of the additional material includedifferentially heating the material and the additional material with thelight beam.

The defect may include a subsurface defect or a partially subsurfacedefect. In some embodiments, the material may include a device film. Insuch an embodiment, removing the portion of the material does notsubstantially alter an aspect ratio of device features on the substrate.In some embodiments, the method may also include analyzing the defect todetermine a characteristic of the defect. In one embodiment, the methodmay include analyzing the defect using the electron beam to determine acharacteristic of the defect. In a different embodiment, the method mayinclude analyzing the defect using an x-ray analysis system to determinea characteristic of the defect. In one embodiment, the characteristic ofthe defect may include a composition. Each of the embodiments of themethod described above may include any other step(s) described herein.

An additional embodiment relates to a different system that isconfigured to prepare a substrate for analysis. This system includes achemical delivery subsystem that is configured to deliver one or morechemicals to a substrate. The one or more chemicals may include afluorine-based chemistry, a chlorine-based chemistry, a bromine-basedchemistry, or an oxygen-based chemistry. The system also includes anelectron and light delivery subsystem configured to deliver an electronbeam to the substrate coaxially with a light beam. The one or morechemicals in combination with the electron beam and the light beamremove a portion of a material on the substrate proximate to a defect.

The defect may include a subsurface defect or a partially subsurfacedefect. In an embodiment, the material may include a device film. Insuch an embodiment, the one or more chemicals in combination with theelectron beam and the light beam do not substantially alter an aspectratio of device features on the substrate. The portion of the materialthat is removed may have an area that is equal to or less than about 10μm by about 10 μm.

In one embodiment, the electron and light delivery subsystem may includea laser that is configured to generate the light beam. The electron andlight delivery subsystem also includes an electron column. The electroncolumn may include an optical window configured to allow the light beamto enter the electron column. In addition, the electron and lightdelivery subsystem may include a mirror with an aperture formed throughthe mirror. The electron beam passes through the aperture, and the lightbeam is reflected from the mirror such that the light beam is coaxialwith the electron beam.

The electron and light delivery subsystem is also configured such thatthe light beam heats the material. In addition, the electron and lightdelivery subsystem may be configured such that the light beam heats ahorizontal surface of the material and does not substantially heat avertical surface of the material. In some embodiments, the one or morechemicals in combination with the electron beam and the light beam mayalso remove a portion of an additional material on the substrateproximate to the defect. The additional material is different than thematerial and is formed under the material. In one such embodiment, theelectron and light delivery subsystem may be configured such that thelight beam differentially heats the material and the additionalmaterial.

In some embodiments, the system may also include an analysis subsystemthat is configured to measure a characteristic of the defect. In oneembodiment, the electron and light delivery subsystem may be configuredto measure a characteristic of the defect using the electron beam.Therefore, the electron and light delivery subsystem may function as ananalysis subsystem. In another embodiment, the analysis subsystem mayinclude an x-ray analysis system. The characteristic of the defect maybe a composition of the defect. Each of the embodiments of the systemdescribed above may be further configured as described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages of the present invention may become apparent to thoseskilled in the art with the benefit of the following detaileddescription of the preferred embodiments and upon reference to theaccompanying drawings in which:

FIG. 1 is a schematic diagram illustrating a partial perspective view ofa feature on a substrate, which is exposed to an electron beam;

FIG. 2 is a schematic diagram illustrating a partial perspective view ofthe substrate of FIG. 1 in which a portion of the feature is removed bythe electron beam to expose a cross-sectional profile of a remainingportion of the feature;

FIG. 3 is a schematic diagram illustrating partial perspective views ofother features in which a portion of the features is removed by anelectron beam to expose a cross-sectional profile of a remaining portionof the features;

FIGS. 4-7 are schematic diagrams illustrating side views of differentembodiments of a system configured to measure a characteristic of asubstrate;

FIG. 8 is a schematic diagram illustrating a partial cross-sectionalview of a defect on a substrate, which is exposed to chemical etching incombination with an electron beam;

FIG. 9 is a schematic diagram illustrating a partial cross-sectionalview of the substrate of FIG. 8 in which a portion of a material on thesubstrate proximate to the defect is removed;

FIG. 10 is a schematic diagram illustrating a partial top view of thesubstrate of FIG. 9;

FIG. 11 is a schematic diagram illustrating a partial cross-sectionalview of the substrate of FIG. 9 and an electron beam used to determine acharacteristic of the defect;

FIG. 12 is a schematic diagram illustrating a partial cross-sectionalview of a defect on a substrate;

FIG. 13 is a schematic diagram illustrating a partial cross-sectionalview of the substrate of FIG. 12 in which a portion of a material on thesubstrate proximate to the defect is removed;

FIG. 14 is a schematic diagram illustrating a partial cross-sectionalview of the substrate of FIG. 13 in which a portion of an additionalmaterial on the substrate proximate to the defect is removed;

FIG. 15 is a schematic diagram illustrating a side view of an embodimentof a system configured to prepare a substrate for analysis;

FIG. 16 is a schematic diagram illustrating a partial cross-sectionalview of a defect on a substrate, which is exposed to chemical etching incombination with an electron beam and a light beam;

FIG. 17 is a schematic diagram illustrating a partial cross-sectionalview of a defect on a substrate, in which a portion of a material on thesubstrate proximate to the defect has been removed, and an electron beamand a light beam that may be used to determine a characteristic of thedetect;

FIG. 18 is a schematic diagram illustrating a partial cross-sectionalview of a system configured to prepare a substrate for analysis;

FIG. 19 is a schematic diagram illustrating a side view of focal spotson a substrate by off-axis and coaxial laser delivery;

FIG. 20 is a schematic diagram illustrating a perspective top view ofone embodiment of a portion of a system configured to prepare asubstrate for analysis; and

FIG. 21 is a schematic diagram illustrating a partial cross-sectionalview of an embodiment of a portion of a system configured to prepare asubstrate for analysis.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and may herein be described in detail. Thedrawings may not be to scale. It should be understood, however, that thedrawings and detailed description thereto are not intended to limit theinvention to the particular form disclosed, but on the contrary, theintention is to cover all modifications, equivalents and alternativesfalling within the spirit and scope of the present invention as definedby the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As used herein, the term “substrate” is generally defined as a wafer ora reticle. As used herein, the term “wafer” generally refers to asubstrate formed of a semiconductor or non-semiconductor material.Examples of such a semiconductor or non-semiconductor material include,but are not limited to, monocrystalline gallium arsenide, and indiumphosphide. Such substrates may be commonly found and/or processed insemiconductor fabrication facilities.

A wafer may include only the substrate. Such a wafer is commonlyreferred to as a “virgin wafer.” Alternatively, a wafer may include oneor more layers formed upon a substrate. For example, such layers mayinclude, but are not limited to, a resist, a dielectric material, and aconductive material. A resist or a “photoresist” may include anymaterial that may be patterned by an optical lithography technique, ane-beam lithography technique, or an X-ray lithography technique.Examples of a dielectric material include, but are not limited to,silicon dioxide, silicon nitride, silicon oxynitride, and titaniumnitride. Additional examples of a dielectric material include “low-k”dielectric materials such as Black Diamond™ which is commerciallyavailable from Applied Materials, Inc., Santa Clara, Calif., and CORAL™commercially available from Novellus Systems, Inc., San Jose, Calif.,“ultra-low k” dielectric materials such as “xerogels,” and “high-k”dielectric materials such as tantalum pentoxide. In addition, examplesof a conductive material include, but are not limited to, aluminum,polysilicon, and copper.

One or more layers formed on a wafer may be patterned or unpatterned.For example, a wafer may include a plurality of dies having repeatablepattern features. Formation and processing of such layers of materialmay ultimately result in completed semiconductor devices. As such, awafer may include a substrate on which not all layers of a completesemiconductor device have been formed or a substrate on which all layersof a complete semiconductor device have been formed. The term“semiconductor device” is used interchangeably herein with the term“integrated circuit.” In addition, other devices such asmicroelectromechanical (MEMS) devices and the like may also be formed ona wafer.

A “reticle” or a “mask” is generally defined as a substantiallytransparent substrate having substantially opaque regions formed thereonand configured in a pattern. The substrate may include, for example, aglass material such as quartz. The substantially opaque regions may beformed of a material such as chromium. A reticle may be disposed above aresist-covered wafer during an exposure step of a lithography processsuch that the pattern on the reticle may be transferred to the resist.For example, substantially opaque regions of the reticle may protectunderlying regions of the resist from exposure to an energy source. Manydifferent types of reticles are known in the art, and the term reticleas used herein is intended to encompass all types of reticles.

As used herein, the term “feature” generally refers to any structureformed on a substrate that has sonic lateral extent in three-dimensions(i.e., a width as well as a height). Examples of features includepatterned structures formed on semiconductor wafers. Patternedstructures may be formed on semiconductor wafers using any process knownin the art (e.g., lithography and etch). The features may be formed ofany material known in the art such as a resist, a conductive material,and an insulating material.

Turning now to the drawings, it is noted that FIGS. 1-21 are not drawnto scale. In particular, the scale of some of the elements of thefigures is greatly exaggerated to emphasize characteristics of theelements. It also noted that FIGS. 1-21 are not drawn to the same scale.Elements shown in more than one figure that may be similarly configuredhave been indicated using the same reference numerals.

Turning now to the drawings, FIGS. 1 and 2 illustrate a method formeasuring a characteristic of a substrate. As shown in FIG. 1, feature10 is formed on substrate 12. The feature may be a photoresist featurein one embodiment. However, the feature may be any of the featuresdescribed above. For example, the feature may be a conductive feature oran insulating feature. Feature 10 is shown as a line. However, it is tobe understood that the feature may have any shape. In one embodiment,the substrate may be a product wafer. As such, the feature may be formedin a test area on the product wafer or in a device area on the productwafer. In other words, the feature may be a test feature or a devicefeature. However, the substrate may include any of the other substratesdescribed above.

As further shown in FIG. 1, the method includes using electron beam 14to remove portion 10 a of feature 10 thereby exposing a cross-sectionalprofile of a remaining portion of feature 10. In other words, thistechnique uses an electron beam to remove material from a substratethereby revealing the orthogonal profile of a feature on the substrate.For example, as shown in FIG. 2, after portion 10 a of feature 10 isremoved using electron beam 14, cross-sectional profiles 16 of remainingportions 10 b and 10 c of feature 10 are exposed. As shown in FIGS. 1and 2, portion 10 a of feature 10 that is removed is substantiallyconfined to an area of the feature that is illuminated by electron beam14. In addition, removing portion 10 a of feature 10 does not remove anyportion of substrate 12. In this manner, portion 10 a of feature 10 canbe removed without damaging or destroying substrate 12. In addition, theelectron beam will not contaminate the substrate. Therefore, the methodsand systems described herein for measuring a characteristic of asubstrate are advantageous over other currently used methods and systemssince the methods and systems described herein do not contaminate ordestroy the substrate.

As further shown in FIGS. 1 and 2, removing portion 10 a of feature 10using electron beam 14 does not substantially deform remaining portions10 b and 10 c of the feature. In other words, remaining portions 10 band 10 c have substantially the same dimensions and three-dimensionalprofiles as those of feature 10. FIG. 3 also illustrates features havingother shapes of which a portion has been removed by the method describedherein. As shown in FIG. 3, remaining portions 18 a and 18 b of feature18 have substantially the same dimensions and three-dimensional profilesas those of the original feature. In addition, remaining portions 20 aand 20 b of feature 20 have substantially the same dimensions andthree-dimensional profiles as those of the original feature. As shown inFIG. 3, a portion of differently shaped features can be removed asdescribed herein, and the shape of the feature that is being etched bythe electron beam will not have any effect on the quality of theremaining portions of the feature.

The quality of the material removal (e.g., horizontal linearity,sidewall orthogonality, material removal rate, etc.) is generally afunction of electron beam focus quality, landing energy, etch gasavailability, and beam dwell time. Therefore, these parameters of theelectron beam can be altered to optimize the material removal and thequality of the remaining portions of the feature. These parameters mayalso vary depending on, for example, characteristics of the feature(e.g., size and composition) and characteristics of the substrate (e.g.,composition, underlying layers, etc.). In this manner, the methods andsystems described herein can be used to produce an exposedcross-sectional profile of a feature that is particularly suitable formeasurement since the remaining portions of the feature retain theoriginal characteristics of the feature. Therefore, the methods andsystems described herein for measuring a characteristic of a substrateare advantageous over other currently used methods and systems since themethods and systems described herein do not cause deformation of thefeatures on the substrate.

The method also includes measuring a characteristic of at least one ofthe cross-sectional profiles 16 of remaining portions 10 b and 10 c offeature 10. For example, measuring a characteristic of cross-sectionalprofiles 16 may be performed using electron beam 14. In such an example,the electron beam may be used to image one of the cross-sectionalprofiles using a scanning electron microscopy technique. Thecharacteristic that is measured may include a three-dimensionalcharacteristic of the feature (e.g., a critical dimension of thefeature, a height of the feature, a sidewall angle or slope of thefeature, a three-dimensional profile of the feature, or any othercharacteristic of the cross-sectional profile that may be measured usinga scanning electron microscopy technique). For example, as shown in FIG.3, three-dimensional characteristics of cross-sectional profiles 22 and24 of remaining portions 18 b and 20 b, respectively, that may bemeasured using scanning electron microscopy include, but are not limitedto, critical dimension 26, height 28, and slope 30. Therefore, themethods are particularly useful for three-dimensional metrology of afeature formed on a substrate. In addition, three-dimensional metrologyof the feature may be performed while the feature is etched (e.g., usingthe same electron beam).

If the same electron beam is used to remove the portion of the featureand to measure a characteristic of the cross-sectional profile, theparameters of the subsystem used to deliver the electron beam may bechanged between removal and measurement to change one or morecharacteristics of the electron beam (e.g., energy, focus, etc.). Theparameters of the electron beam may vary depending upon, for example,the size of the feature, the composition of the feature, the compositionof the substrate, or the composition of the layer of the substrate uponwhich the feature is formed. Selection of appropriate parameters forremoval and measurement will be obvious to one of ordinary skill theart. In particular, the characteristics of the electron beam (andtherefore, the parameters of the electron delivery subsystem) may beselected such that the rate at which the portion of the feature isremoved enhances the perpendicularity of the exposed cross-sectionalprofiles. In other words, the characteristics of the electron beam maybe selected to avoid under-etch or over-etch of the remaining portionsof the feature.

When measuring a characteristic of the cross-sectional profile of theremaining portion of the feature with the same electron beam that isused for removal, the substrate may be tilted relative to the electronbeam after the portion of the feature is removed and before thecharacteristic is measured. In this manner, the electron beam may bearranged at an appropriate viewing angle with respect to the remainingportion of the feature. The substrate may be tilted by altering theposition of a stage (not shown) upon which the substrate is disposedbetween removal of the portion of the feature and measurement.Alternatively, or in addition, the electron beam may be tilted relativeto the substrate after the portion of the feature is removed and beforemeasurement such that the electron beam is at an appropriate viewingangle during measurements. The electron beam may be tilted by alteringone or more parameters of an electron delivery subsystem that isconfigured to deliver the electron beam to the substrate.

In a different embodiment, removing the portion of the feature may beperformed using one electron beam, and measuring a characteristic of across-sectional profile of the feature may be performed using adifferent electron beam. In such an embodiment, the different electronbeam may be arranged at a predetermined tilt position with respect tothe substrate. In this manner, after a substrate is placed on a stagecoupled to the different electron beam, the position of the stage maynot have to be altered before a measurement can be performed.

In one such embodiment, one electron beam may remove a portion of onefeature on the substrate while the other electron beam is measuring acharacteristic of a cross-sectional profile of a different feature onthe substrate. The cross-sectional profile being measured may have beenpreviously exposed using the first electron beam. Therefore, differentelectron beams may perform different functions (e.g., removal andmeasurement) on a substrate at the same time. In other words, asubstrate may be exposed to two or more electron beams while beingdisposed on the same stage.

In another example, one electron beam may be used to perform removal andmeasurement on one feature while another electron beam is performingremoval and measurement on another feature. In a different example, oneof the electron beams may remove a portion of a feature on one substratewhile another electron beam measures a feature on another substrate.Each of the embodiments of the method described above may include anyother step(s) described herein.

Additional embodiments relate to a system configured to measure acharacteristic of a substrate according to the method described above.FIG. 4 illustrates an embodiment of one such system. As shown in FIG. 4,the system includes electron delivery subsystem 32. Electron deliverysubsystem 32 is configured to deliver an electron beam (not shown) to asubstrate (not shown). The system also include stage 34 upon which asubstrate may be disposed during removal and measurement. Stage 34 mayinclude any appropriate stage known in the art. The electron deliverysubsystem may be configured as an electron column. The electron deliverysubsystem may include any appropriate electron column known in the art.The electron delivery subsystem may also include additional components(not shown) coupled to the electron column. The additional componentsmay include, for example, components configured to control the electroncolumn. The system may also include other components such as a processor(not shown) coupled to the electron column and optionally the stage. Theprocessor may be configured to control the electron column and the stageas further described herein.

The electron beam delivered to the substrate by electron deliverysubsystem 32 can be used to remove a portion of a feature on thesubstrate thereby exposing a cross-sectional profile of a remainingportion of the feature as described above. The feature may include aphotoresist feature or any of the other features described above. Thesubstrate may be a product wafer or any other substrate described above.As described above, removal of the portion of the feature by theelectron beam does not substantially deform the remaining portion of thefeature, as shown in FIGS. 2 and 3. In addition, the portion of thefeature that is removed is substantially confined to an area of thefeature illuminated by the electron beam, as described further above andas shown in FIGS. 1 and 2.

The electron beam delivered to the substrate by electron deliverysubsystem 32 can also be used to measure a characteristic of across-sectional profile of the remaining portion of the feature. Thecharacteristic may include any three-dimensional characteristic of thefeature described above. In one embodiment of the system shown in FIG.4, the system may be configured to tilt the substrate relative to theelectron beam between removal and measurement. For example, the systemmay include a processor or a controller coupled to stage 34. Theprocessor or controller may be configured to alter a position of stage34 thereby altering a position of the substrate relative to the electronbeam. In this manner, the system may be configured to control the stagesuch that the substrate may be arranged at an appropriate angle withrespect to the electron beam for both removal and measurement.

In another embodiment, the system shown in FIG. 4 may be configured totilt an electron beam of electron delivery subsystem 32 between removaland measurement. For example, the system may include a processor or acontroller coupled to electron delivery subsystem 32. The processor orcontroller, possibly in combination with one or more components of theelectron delivery subsystem, may be configured to alter one or moreparameters of the electron column thereby altering a position of theelectron beam with respect to the substrate. As such, the system may beconfigured to control the electron delivery subsystem such that theelectron beam may be arranged at an appropriate angle with respect tothe substrate for both removal and measurement.

FIG. 5 illustrates another embodiment of a system configured to measurea characteristic of a substrate. In this embodiment, the system includestwo electron delivery subsystems 36 and 38. Each of the electrondelivery subsystems is configured to deliver an electron beam to asubstrate (not shown). For example, electron delivery subsystem 36 isconfigured to deliver an electron beam (not shown) to a substrate thatis disposed on stage 40, and electron delivery subsystem 38 isconfigured to deliver an electron beam (not shown) to a substrate thatis disposed on stage 42. Stages 40 and 42 may include any appropriatestages known in the art. In addition, stages 40 and 42 may be the sameor different types of stages.

Each of the electron delivery subsystems may be generally configured asan electron column. The electron delivery subsystems may include anyappropriate electron columns known in the art. In addition, the electroncolumns of the two electron delivery subsystems may be configuredsimilarly or differently. The electron delivery subsystems may alsoinclude additional components (not shown) coupled to the electroncolumns. The additional components may include, for example, componentsconfigured to control the electron beams. The system may also includeother components such as one or more processors (not shown) coupled toone or more of the electron columns and one or more of the stages. Theprocessor may be configured to control the electron column and the stageas further described herein.

The electron beam delivered to the substrate by electron deliverysubsystem 36 can be used for removal as described above. The electronbeam delivered to the subsystem by electron delivery subsystem 38 can beused for measurements as described above. In one embodiment of thesystem shown in FIG. 5, electron delivery subsystem 38 may be configuredsuch that the electron beam that it delivers to the substrate isarranged at a predetermined tilt position with respect to the substrate.In this manner, a position of stage 42 my not have to be substantiallyaltered prior to measurements.

In the system shown in FIG. 5, therefore, one electron deliverysubsystem may be used for removal, and another electron deliverysubsystem may be used for measurement. In addition, as shown in FIG. 5,each of the electron delivery subsystems is coupled to a differentstage. Therefore, after removal of a portion of a feature on a substrateby, for example, an electron beam delivered by electron deliverysubsystem 36, a substrate handler (not shown) may remove the substratefrom stage 40 and move the substrate to stage 42 such that an electronbeam delivered by electron delivery column 38 can measure acharacteristic of the feature. Therefore, in one embodiment, the twoelectron delivery subsystems may be coupled by a common substratehandler. In addition, as shown in FIG. 5, electron delivery columns 36and 38 may be arranged within one housing 44.

In the embodiment described above, therefore, one electron deliverysubsystem may be dedicated to material removal, and the other electrondelivery subsystem may be dedicated to measurement. However, it is to beunderstood that both electron delivery subsystems may also be configuredto perform both material removal and measurement, as described abovewith respect to electron delivery subsystem 32. In either embodiment,the system shown in FIG. 5 may be configured to process two substratesat the same time. For example, one electron delivery subsystem mayperform material removal on one feature on one substrate while the otherelectron delivery subsystem performs a measurement of another feature onanother substrate. In another example, one of the electron deliverysubsystems can remove a portion of a feature on a substrate and thenmeasure a three-dimensional characteristic of the feature while theother electron delivery subsystem is similarly processing a differentsubstrate.

As described above, the two electron delivery subsystems may be coupledby a common substrate handler or may be arranged within one housing. Thetwo electron delivery subsystems may, however, be coupled in a differentmanner. For example, in one embodiment shown in FIG. 6, electrondelivery subsystem 36 may be coupled to electron delivery subsystem 38by common processor 46. Processor 46 may be coupled to electron deliverysubsystem 36 by transmission medium 48. Processor 46 may also be coupledto electron delivery subsystem 38 by transmission medium 50.Transmission media 48 and 50 may include any appropriate transmissionmedia known in the art and may include “wired” and “wireless” portions.Processor 46 may be configured to perform the various functionsdescribed herein. In addition, processor 46 may be configured to receivemeasurement data from electron delivery subsystem 36 and/or electrondelivery subsystem 38. Processor 46 may be configured to process themeasurement data using any method known in the art. For example,processor may receive image data from electron delivery subsystem 36and/or electron delivery subsystem 38. Processor 46 may also use one ormore algorithms to extract edges of the feature from the image data andto determine one or more characteristics of the feature from the imagedata.

In another embodiment shown in FIG. 7, electron delivery subsystem 36may be coupled to electron delivery subsystem 38 by transmission medium52. Transmission medium 52 may include any appropriate transmissionmedium known in the art and may include “wired” and “wireless” portions.The transmission medium serves as an information link between the twoelectron delivery subsystems. In addition, electron delivery subsystems36 and 38 may have their own processors, wafer handlers, housings, powersources, etc. (not shown). As such, each electron delivery subsystem maybe configured as a preparation (e.g., material removal) and/ormeasurement system completely separate from the other subsystem exceptfor the transmission medium. In addition, electron delivery subsystem 36may be located remotely from electron delivery subsystem 38.

However, regardless of their locations, electron delivery subsystem 36and electron delivery subsystem 38 may be coupled by transmission medium52. In one particular embodiment, a processor of electron deliverysubsystem 36 may be coupled by transmission medium 52 to a processor ofelectron delivery subsystem 38. In this manner, measurements and otherinformation may be sent between processors of the subsystems. Forexample, electron delivery subsystem 36 may send a location of a featurethat has been etched as described above to electron delivery subsystem38. Electron delivery subsystem 38 may then use the information tolocate the feature to be measured and then carry out the measurements.The system shown in FIG. 5 may be further configured as describedherein. In addition, the processors of subsystems 36 and 38 may beconfigured as described further herein.

Although the embodiments of the system shown in FIGS. 4-7 include one ortwo electron delivery subsystems, it is to be understood that in someembodiments a system may include more than two electron deliverysubsystems. In this manner, more than two electron beams may bedelivered to substrates at the same time for feature etching and/ormeasurement. In addition, although in the embodiments of the systemsshown in FIGS. 4-7 each electron delivery subsystem is coupled to adifferent stage, it is to be understood that more than one electrondelivery subsystem may be coupled to the same stage in some embodiments.In this manner, two or more electron beams may be delivered to onesubstrate at substantially the same time. As such, feature etchingand/or measurement may be carried out at more than one location on thesubstrate at substantially the same time. The systems shown in FIGS. 4-7may be further configured as described herein.

Additional methods and systems are described herein that may be used forremoving device film layers (de-layering) at selective locations in acontrollable fashion. Such de-layering is critical for defect review andanalysis during the device fabrication process. As described furtherabove, current techniques for de-layering include ion beam etching,laser ablative etching, and mechanical abrasion using micro-tip. Thesetechniques have disadvantages such as causing changes in the optical,electrical, and mechanical properties of the etched features andsurrounding areas and contamination of the substrate, which effectivelydestroys the substrate.

Electron beam assisted chemical etching as described further herein hasmany advantages over these techniques. For example, using an electronbeam instead of an ion beam for etching eliminates the ion contaminationand the collateral damage that the ion beam causes to surrounding areas.Therefore, the methods and systems described herein are compatible withfront end of the line (FEOL) processing and back end of the line (BEOL)processing, and wafers that have been de-layered as described herein canbe returned to the process line. In addition, another advantage ofelectron beam assisted chemical etching is the high degree of etchselectivity and endpoint detection. Selective electron beam assistedchemical etching with fluorine, chlorine, bromine, and oxygen basedchemistries has been developed for most of the film layers in DRAMmemory devices, logic devices, and photoresist. Furthermore, since themethods and systems described herein have a relatively high throughput,the time in which the root cause of defects can be correctly identifiedusing these methods and systems may be significantly lower thancurrently used methods and systems.

FIGS. 8-10 illustrate an embodiment of a method for preparing asubstrate for analysis. As shown in FIG. 8, defect 54 is formed onsubstrate 56. Substrate 56 may include any of the substrates describedabove. In this example, material 58 is formed on substrate 56. Material58 may include any material known in the art such as a photoresist, aconductive material, or an insulating material. Although only onematerial is shown on substrate 56 in FIGS. 8-10, it is to be understoodthat two or more materials may be formed on the substrates describedherein. Some of the materials may be unpatterned as shown in FIGS. 8-10,or may be patterned as described above. As shown in FIG. 8, defect 54 isa partially subsurface defect. In other words, a portion of defect 54 islocated below upper surface 60 of material 58. However, the methods andsystems described herein may also be performed on substrates thatinclude a completely subsurface defect (such as that shown in FIG. 12and described further below) or a surface defect (i.e., a defect thatdoes not reside below an upper surface of the substrate). In addition,although defect 54 is shown as a particle defect, it is to be understoodthat the defect may be any defect known in the art.

As shown in FIG. 8, a portion of material 58 is exposed to chemicaletching in combination with electron beam 64. The chemical etching mayinclude exposing substrate 56 to etch chemistry 62. In sonicembodiments, the etch chemistry may include a fluorine-based chemistry,a chlorine-based chemistry, a bromine-based chemistry, or anoxygen-based chemistry. These etch chemistries may include one or morechemicals. For example, a fluorine-based etch chemistry may include oneor more fluorocarbons possibly in combination with other chemicals suchas argon. Many such chemistries are known in the art, and the etchchemistry may include any such chemistry. The selection of an etchchemistry may vary depending on, for example, the composition ofmaterial 58, the composition of defect 54, and the composition of anyother materials on the substrate that might be exposed to the etchchemistry. For example, the etch chemistry is preferably selected suchthat it does not substantially alter or etch the defect, particularlysince the defect is to be analyzed after de-layering as furtherdescribed herein. In addition, the etch chemistry is preferably selectedsuch that it has good selectivity for material 58 (i.e., it etchesmaterial 58 faster than it etches other materials on substrate 56) and,if possible, such that it has good anisotropy (i.e., it etcheshorizontal surfaces of material 58 faster than it etches verticalsurfaces of material 58). Furthermore, the etch chemistry is preferablyselected such that it does not substantially etch materials on thesubstrate other than material 58. In this manner, the etch chemistry maynot damage the substrate or other materials or features exposed to theetch chemistry. In addition, the selectivity of the etch can be alteredby changing one or more parameters of the electron beam.

As shown in FIG. 9, chemical etching in combination with electron beam64 removes portion 66 of material 58 proximate to defect 54. As furthershown in FIG. 9, the remaining portion of the material proximate to thedefect has upper surface 68 that is approximately commensurate with alower surface of defect 54. However, in other embodiments, the portionof the material proximate the defect may be “over-removed” or“over-etched” such that upper surface 68 is lower than a lowermostsurface of the defect. The depth to which the material proximate to thedefect is removed may vary depending on, for example, the analysis thatis to be performed on the defect.

As shown in FIG. 10, portion 66 of material 58 that is removed proximatedefect 54 laterally surrounds defect 54. In this manner, the portion ofthe material that is removed has an area in which the defect resides. Assuch, all sides of the defect may be exposed after de-layering such thatanalysis of the defect may be performed from various angles with respectto the defect. In one embodiment, the portion of the material that isremoved has an area that is equal to or less than about 10 μm by about10 μm. Therefore, the area on the substrate in which material is removedis relatively small, particularly when compared to the amount ofmaterial that is typically removed by other de-layering processes. Inthis manner, the methods described herein may be performed on productwafers since in most instances removing material from such a small areaon the product wafer should not adversely affect the product wafer as awhole.

The area of the portion of the material that is removed may varydepending on, for example, the area on the substrate that is illuminatedby the electron beam. For example, in the methods and systems describedherein, etching takes place only in the presence of etchant gases incombination with the electron beam. In this manner, the diameter of theelectron beam, and thereby the area of the removed material, may bealtered depending on, for example, the lateral dimensions of the defect,the area that is selected for removal, the analysis that is to becarried out on the detect, the characteristics of the material beingremoved, and/or the characteristics of the substrate. In one particularexample, the area of the material that is removed is preferably kept ata minimum (to avoid damaging or destroying neighboring structures ifpresent) while allowing enough material removal around the defect foranalysis to be successfully completed.

The method may also include analyzing defect 54 to determine acharacteristic of the defect. The characteristic of the defect that isdetermined may include any characteristic that may be of interest suchas dimensions (height and width), profile, composition, roughness, etc.Therefore, the characteristic of the defect that is to be determined maydetermine what analysis is performed on the defect. In one embodiment,analyzing the defect may be performed using an electron beam. In oneparticular embodiment, as shown in FIG. 11, electron beam 64 that wasused to remove portion 66 of material 56 proximate defect 54 may also beused to analyze defect 54. Parameters of the electron beam used toremove the portion of the material may be different than those that areused to analyze the defect. In one such embodiment, the electron beammay be used to image the defect using a technique such as scanningelectron microscopy. The image of the defect may then be used for defectreview or to determine characteristics of the defect. In anotherembodiment, electron beam 64 may be used to image the defect as thematerial is being removed. In this manner, the defect and thede-layering process can be monitored and recorded, possibly in realtime, which may provide further information about the defect, thematerial proximate the defect, and the de-layering process. Suchinformation may also be used to determine an endpoint of the processand/or to optimize the de-layering process.

In another embodiment, the electron beam may be used to determine acomposition of the defect using a technique such as energy dispersivex-ray spectroscopy (EDX or EDS) or Auger electron spectroscopy (AES).Once the defect composition has been determined, the de-layering methodsdescribed herein may be altered to maximize the selectivity between thedefect and the surrounding films. Generally, in the EDX technique, abeam of electrons is directed to a surface of the defect. The defect mayemit secondary electrons and a characteristic x-ray in response to thedirected beam of electrons. The characteristic x-ray may be detected bya semiconductor x-ray detector and may be subjected to energy analysis.The x-ray spectrum may be analyzed to determine a composition of thedefect. Examples of EDX systems and methods are illustrated in U.S. Pat.No. 4,559,450 to Robinson et al., U.S. Pat. No. 6,072,178 to Mizuno, andU.S. Pat. No. 6,084,679 to Steffan et al., and are incorporated byreference as if fully set forth herein.

In another embodiment, an x-ray analysis system (not shown) may be usedto determine a characteristic of the defect. For example, a compositionof a defect can be determined using a technique such as x-rayphotoelectron spectroscopy (XPS or ESCA) or x-ray fluorescencespectrometry (XRF). In another example, an x-ray reflectance (XRR)technique may be used to measure a characteristic of a defect such as aconcentration of an element in a defect. Examples of x-ray reflectancemethods and systems are illustrated in U.S. Pat. No. 5,740,226 to Komiyaet al., U.S. Pat. No. 6,040,198 to Komiya et al., and U.S. Pat. No.6,633,831 to Nikoonahad et al., which are incorporated by reference asif fully set forth herein. The x-ray analysis system may be configuredas described in these patents.

In other embodiments, analysis of the defect may be performed using anyother analytical technique known in the art. For example, the defect maybe analyzed using secondary ion mass spectroscopy (SIMS). SIMS generallyinvolves removing material from a sample by sputtering ions from thesurface of the sample and analyzing the sputtered ions by massspectrometry. Examples of SIMS techniques are illustrated in U.S. Pat.No. 4,645,929 Criegern et al., U.S. Pat. No. 4,912,326 to Naito, U.S.Pat. No. 6,078,0445 to Maul et al., and U.S. Pat. No. 6,107,629 toBenninghoven et al., and are incorporated by reference as if fully setforth herein. The analysis system may be configured as described inthese patents.

FIGS. 12-14 illustrate another embodiment of a method for preparing asubstrate for analysis. As shown in FIG. 12, defect 70 is formed onsubstrate 72. Substrate 72 may include any of the substrates describedabove. In this example, materials 74 and 76 are formed on substrate 72.Materials 74 and 76 may be formed on substrate 72 using any processknown in the art (e.g., deposition, plating, etc.) or a combination ofprocesses (e.g., deposition and chemical-mechanical polishing).

As shown in FIG. 12, material 76 is formed under material 74. Materials74 and 76 may include any material known in the art such as aphotoresist, a conductive material, or an insulating material. Materials74 and 76 are different materials. In other words, materials 74 and 76have different compositions. For example, material 74 may be aninsulating material, and material 76 may be a conductive material.Alternatively, material 74 may be one type of insulating material, andmaterial 76 may be a different type of insulating material. Althoughonly two materials are shown formed on substrate 72 in FIGS. 12-14, itis to be understood that many materials may be formed on the substratesdescribed herein. The materials may be unpatterened as shown in FIGS.12-14, and/or may be patterned as described above.

As shown in FIG. 12, defect 70 is a subsurface defect. In other words,defect 70 is located entirely below upper surface 78 of material 74.However, the methods and systems described herein may also be performedon substrates that include a partially subsurface defect (such as thatshown in FIG. 8 and described further above) or a surface defect (i.e.,a defect that does not reside below an upper surface of the substrate).Although defect 70 is shown as a particle defect, it is to be understoodthat the methods and systems described herein may be used for substrateshaving any type of defect.

As shown in FIG. 13, the method includes removing portion 80 of material74 proximate to defect 70 using chemical etching in combination with anelectron beam (not shown). The chemical etching may include exposingsubstrate 72 to an etch chemistry (not shown). The etch chemistry mayinclude any of the etch chemistries described herein. In addition, theselectivity of the etch can be altered by changing one or moreparameters of the etch chemistry and/or one or more parameters of theelectron beam. As shown in FIG. 13, portion 80 of material 74 proximateto the defect may be completely removed to expose upper surface 82 ofmaterial 76. As further shown in FIG. 13, removing portion 80 ofmaterial 74 has only partially exposed defect 70. Therefore, in someembodiments, as shown in FIG. 14, the method may also include removingportion 84 of material 76 proximate to defect 70 using chemical etchingin combination with an electron beam (not shown).

Since materials 74 and 76 are different types of materials, parametersof the chemical etching and the electron beam may be different forremoval of the portion of material 74 and for removal of the portion ofmaterial 76. For instance, different etch chemistries may be used toremove material 74 and 76. In one example, a fluorine-based etchchemistry may be used to remove material 74, and a chlorine-based etchchemistry may be used to remove material 76. In particular, the etchchemistries may be selected for removal of each of the materials basedon the composition and other characteristics of the materials.Preferably, the portions of the different materials are removed indifferent steps of one etch process that can be carried out in one etchchamber. In addition, the portions of the different materials may beremoved in the different steps using the same electron beam. One or moreparameters of the electron beam can be altered between the removal stepssuch that the electron beam may be optimized for removal of both of thedifferent materials. However, it is to be understood that in someinstances, removal of the portions of the different materials may becarried out in different etch processes that are performed in differentetch chambers possibly in the same etch tool. Obviously, such etchprocesses would be carried out with different electron beams, which mayalso have parameters that are optimized for removal of the differentmaterials.

As shown in FIG. 14, the remaining portion of the material proximate tothe defect has an upper surface 86 that is approximately commensuratewith a lower surface of defect 70. However, in other embodiments,portion 84 of material 76 proximate the defect may be “over-removed” or“over-etched” such that upper surface 86 is lower than a lowermostsurface of the defect. The depth to which the material proximate to thedefect is removed may vary depending on, for example, the analysis thatis to be performed on the defect.

As described further above, portions 80 and 84 of materials 74 and 76that are removed proximate defect 70 laterally surround defect 70. Inthis manner, the portions of the materials that are removed have an areain which the defect resides. As such, all sides of the defect may beexposed after the portions of the materials have been removed such thatanalysis of the defect may be performed from various angles with respectto the defect. In one embodiment, the portions of the materials that areremoved have areas that are equal to or less than about 10 μm by about10 μm. Therefore, the area on the substrate in which materials areremoved is relatively small, particularly when compared to the amount ofmaterial that is typically removed by other de-layering processes. Inthis manner, the methods described herein may be performed on productwafers since in most instances removing material from such a small areaon the product wafer should not adversely affect the product wafer as awhole. The area of the portions of the materials that are removed mayvary depending on, for example, the area on the substrate that isilluminated by the electron beam, as described above.

The method shown in FIGS. 12-14 may also include analyzing defect 70 todetermine a characteristic of the defect. The characteristic of thedefect that is determined may include any of the characteristicsdescribed above. In addition, analysis of the defect may include any ofthe analysis described above.

FIG. 15 illustrates one embodiment of a system that is configured toprepare a substrate for analysis. The system includes chemical deliverysubsystem 88. Chemical delivery subsystem 88 is configured to deliverone or more chemicals (not shown) to substrate 90. In other words, thechemical delivery subsystem is configured to deliver one or morechemicals to process chamber 92 in which substrate 90 is disposed uponstage 94. The one or more chemicals may include any of the chemicalsdescribed above. For example, the one or more chemicals may include afluorine-based chemistry, a chlorine-based chemistry, a bromine-basedchemistry, an oxygen-based chemistry, or any other etch chemistry knownin the art.

Chemical delivery subsystem 88 may include gas source(s) 96 (only one ofwhich is shown in FIG. 15), tubing 98 coupled to gas source(s) 96, avalve 100 coupled to tubing 98, and dispenser 102. The one or morechemicals may flow from gas source(s) 96 through tubing 98 and valve 100to dispenser 102. The dispenser allows the one or more chemicals to bereleased into process chamber 92, preferably in a controllable manner.The gas source(s), tubing, valve, and dispenser may include any suchappropriate components known in the art. The chemical delivery subsystemmay also include many other components known in the art. In addition,the chemical delivery subsystem may have any configuration known in theart. Additional examples of chemical delivery subsystems are illustratedin U.S. Pat. No. 4,842,683 to Cheng et al., U.S. Pat. No. 5,215,619 toCheng et al., U.S. Pat. No. 5,614,060 to Hanawa, U.S. Pat. No. 5,770,099to Rice et al., U.S. Pat. No. 5,882,165 to Maydan et al., U.S. Pat. No.5,849,136 to Mintz et al., U.S. Pat. No. 5,910,011 to Cruse, U.S. Pat.No. 5,926,690 to Toprac et al., U.S. Pat. No. 5,976,310 to Levy, U.S.Pat. No. 6,072,147 to Koshiishi et al., U.S. Pat. No. 6,074,518 toImafuku et al., U.S. Pat. No. 6,083,363 to Ashtiani et al., U.S. Pat.No. 6,089,181 to Suemasa et al., U.S. Pat. No. 6,110,287 to Arai et al.,and U.S. Pat. No. 6,633,831 to Nikoonahad et al., which are incorporatedby reference as if fully set forth herein.

Chemical delivery subsystem 88, process chamber 92 and stage 94 may befurther configured as described in these patents. For example, processchamber 92 may include pressure gauge 104. Pressure gauge 104 may beconfigured to measure a pressure within the process chamber. Thepressure gauge may be coupled to processor 106 by transmission medium108. Transmission medium 108 may include any appropriate transmissionmedium known in the art. In addition, the transmission medium mayinclude “wired” and “wireless” portions. Processor 106 may be configuredto alter one or more parameters of the system depending on the pressuremeasured by pressure gauge 104. In a similar manner, processor 106 maybe coupled to other components of the system (e.g., valve 100) and maybe configured to alter other parameters of the system depending on theprocess being carried out in chamber 92.

The system also includes electron delivery subsystem 110. Electrondelivery subsystem 110 is configured to deliver an electron beam (notshown) to substrate 90. The electron delivery subsystem may be furtherconfigured as described herein. The one or more chemicals delivered bychemical delivery subsystem 88 in combination with the electron beamdelivered by electron delivery subsystem 110 removes a portion of amaterial on the substrate proximate to the defect. The one or morechemicals in combination with the electron beam may remove a portion ofone or more materials as shown in FIGS. 8-10 and 12-14. By-products ofthe reactions between the material(s) and the one or more chemicals incombination with the electron beam are desorbed from the substrate. Thesystem may include one or more pumps (not shown) that are coupled to theprocess chamber. The one or more pumps may be configured to remove suchby-products from the process chamber thereby reducing the possibilitythat the by-products may be deposited onto other areas on the substrate.The pump(s) may be any appropriate pumps known in the art.

The defect, the substrate, the material(s), and the portion of thematerial(s) that are removed may include any of those described above.For example, in one embodiment, the defect may be a subsurface defect ora partially subsurface defect. Alternatively, the defect may be asurface defect. In addition, the portion of the material that is removedmay have an area that is equal to or less than about 10 μm by about 10μm. Furthermore, since the area of the material that is removed isrelatively small, the substrate may be a product wafer. However, thesubstrate may include any other substrates described herein.

In some embodiments, the one or more chemicals delivered by chemicaldelivery subsystem 88 in combination with the electron beam delivered byelectron delivery subsystem 100 may remove a portion of an additionalmaterial on the substrate proximate to the defect, as shown in FIGS.12-14. As further shown in FIGS. 12-14, the additional material (e.g.,material 76) is different than the material (e.g., material 74) and isformed under the material.

The system shown in FIG. 15 may also include an analysis subsystem,which is configured to measure a characteristic of the defect on thesubstrate. The analysis subsystem may be configured to perform one ofthe analysis techniques described herein. The analysis subsystem may beconfigured to determine a composition of the defect or any of the othercharacteristics described herein.

In one embodiment, electron delivery subsystem 110 may be configured tomeasure a characteristic of the defect using the electron beam.Parameters of the electron beam used for removal may be different thanparameters of the electron beam that are used for measurement. Theparameters of the electron beam may be altered between removal andmeasurement by altering one or more parameters of the electron deliverysubsystem. The parameter(s) of the electron delivery subsystem may bealtered or controlled by processor 106 in some embodiments.

In one embodiment, electron delivery subsystem 110 may be configured toimage the defect using a technique such as scanning electron microscopy.In another embodiment, electron delivery subsystem 110 may be used toimage the defect as the material is being removed. In this manner, thedefect and the de-layering process can be monitored and recorded, whichmay provide further information about the defect, the material proximatethe defect, and the de-layering process. Such information may be used tooptimize the de-layering process. In addition, such information may beused to control the de-layering process as it is being carried out(i.e., in real time).

In another example, electron delivery subsystem 110 may be configured todetermine a composition of the defect using a technique such as EDX,which is described further above. In this manner, electron deliverysubsystem 110 may be configured to function as the analysis subsystem.In a different embodiment, the analysis subsystem may include an x-rayanalysis system (not shown) such as those described above or any ofthose known in the art. The analysis subsystem may be coupled to thesystem shown in FIG. 15 in any manner. For example, the analysissubsystem and the system shown in FIG. 15 may be disposed in onehousing, coupled by a common processor, a common substrate handler, acommon power source, a transmission medium, etc. The embodiment of thesystem shown in FIG. 15 may be further configured as described herein.

In the methods and systems described above, de-layering is accomplishedwith a combination of electrons and injected etchant gases at thesubstrate surface. In such embodiments, the de-layering selectivity islargely determined by the etch rates that are obtained by adjusting theetchant gases and the electron beam settings. Although de-layering usingelectron beam assisted chemical etching is a highly effectivede-layering method that offers preferential etching of horizontalsurfaces over vertical surfaces mainly from the effect of the incidentelectron beam, heating of the substrate can further accelerate theetching by accelerating the desorption of reaction by-products at thesurface of the substrate. For example, as further described herein, thesubstrate surfaces can be heated using light to assist the electron andetchant gas reactions.

In one embodiment, a light beam that is coaxially aligned with theelectron beam is used to assist in the etch reaction by heating thesubstrate surface. In particular, the coaxial tight beam amplifies thepreferential etching of the horizontal surfaces by enhancing the effectsof the electron beam on the substrate. For example, by aligning thelight beam coaxially with the electron beam, the light beam canpreferentially heat the horizontal surfaces. In other words, the coaxialtight beam heats the horizontal surfaces on the substrate and does notsubstantially heat the vertical surfaces. This differential surfaceheating is used to accelerate the vertical over lateral etching ofsubstrate surfaces. In particular, the etchant gases preferentially etchthe horizontal surfaces that are irradiated by both electrons and light.In this manner, the addition of light to the de-layering processesdescribed above can increase the anisotropy of the de-layeringprocesses. Such additional anisotropy may be advantageous since theability to remove device films while maintaining the original aspectratio of the device features or any other three-dimensional features iscritical in defect review and analysis.

In addition, by selecting the light beam wavelength, different materialson the substrate can be differentially and preferentially heated. Forexample, the light source may be selected such that the light has awavelength that can be absorbed by the material that is being removedfrom the substrate. In this manner, the wavelength may be selected topreferentially heat material(s) that absorb light at that wavelength. Assuch, the wavelength can be selected to maximize the selectivity betweendifferent materials. Such heating may be particularly desirable duringde-layering of contacts, capacitors, or other three-dimensional featureson the substrate that include two or more materials that aresimultaneously being de-layered.

FIGS. 16-17 illustrate one embodiment of a method for preparing asubstrate for analysis. As shown in FIG. 16, defect 112 is formed onsubstrate 114. Substrate 114 may include any of the substrates describedabove. In this example, material 116 is formed on substrate 114.Material 116 may include any material known in the art such as aphotoresist, a conductive material, or an insulating material. Althoughonly one material is shown on substrate 114 in FIGS. 16-17, it is to beunderstood that many materials may be formed on the substrates describedherein. Some of the materials may be unpatterned as shown in FIGS.16-17, or may be patterned as described above. As shown in FIG. 16,defect 112 is a partially subsurface defect. In other words, a portionof defect 112 is located below upper surface 118 of material 116.However, the methods and systems described herein may also be performedon substrates that include a completely subsurface defect (such as thatshown in FIG. 12) or a surface defect. In addition, although defect 112is shown as a particle defect, it is to be understood that the defectmay be any type of defect known in the art.

As shown in FIG. 16, a portion of material 116 is exposed to chemicalaching in combination with electron beam 120 and light beam 122. Thechemical etching may include exposing substrate 114 to etch chemistry124. In some embodiments, the etch chemistry may include afluorine-based chemistry, a chlorine-based chemistry, a bromine-basedchemistry, or an oxygen-based chemistry. These etch chemistries mayinclude one or more chemicals. Many such chemistries are known in theart, and the etch chemistry may include any such chemistry.

The selection of an etch chemistry may vary depending on, for example,the composition of material 116, the composition of defect 112, and thecomposition of any other materials on the substrate that might beexposed to the etch chemistry. For example, the etch chemistry ispreferably selected such that it does not substantially alter or etchthe defect, particularly since the defect is to be analyzed afterde-layering as further described herein. In addition, the etch chemistryis preferably selected such that it has good selectivity for material116 (i.e., it etches material 116 faster than it etches other materialson substrate 114) and, if possible, such that it has good anisotropy(i.e., it etches horizontal surfaces of material 116 faster than itetches vertical surfaces of material 116). Furthermore, the etchchemistry is preferably selected such that it does not substantiallyetch materials on the substrate other than material 116. In this manner,the etch chemistry may not damage the substrate or other materials orfeatures exposed to the etch chemistry. In addition, the selectivity ofthe de-layering process can be altered by changing one or moreparameters of the electron beam and/or one or more parameters of thelight beam.

As shown in FIG. 16, electron beam 120 is delivered to substrate 114coaxially with light beam 122. In addition, although the diameter ofelectron beam 120 is shown in FIG. 16 to be larger than the diameter oflight beam 122, it is to be understood that a diameter of light beam 122may be approximately equal to or greater than the diameter of electronbeam 120. Light beam 122 may be generated by a laser (not shown).However, the light beam may be generated by any other appropriate lightsource known in the art. In general, light sources that are relativelybright at their operating wavelength(s) may be particularly useful inthe methods described herein. One example of an appropriate laser is aQ-switched laser in the 100 mW range. Another appropriate laser may be aTi-sapphire laser. The light source may also be a single wavelengthlaser or a multiple wavelength laser. In addition, the light beam may begenerated using more than one light source. For example, light fromseveral lasers may be combined into an optical train with a combiner. Inanother example, different light beams may be generated by differentlasers, and the light beam that is delivered to the substrate may varydepending on the material being removed. In this manner, not all of thedifferent light beams may be delivered to the substrate at the sametime.

The wavelength of light beam 122 will vary depending on the materialthat is being removed. For example, the wavelength of light beam 122 maybe selected such that the light can be absorbed by the material. In thismanner, the light beam may heat the material as described above. Inaddition, the light beam may have one wavelength (e.g., monochromaticlight), approximately one wavelength (e.g., near monochromatic light),or more than one wavelength of light polychromatic light or broadbandlight). Examples of appropriate wavelengths include, but are not limitedto, about 1054 nm (near infrared), about 527 nm (visible, green), about350 nm (near ultraviolet), and about 266 nm (ultraviolet). In general,appropriate wavelength(s) may include any wavelength(s) from about 266nm to about 1054 nm.

If light having different wavelengths is delivered to the substrate atthe same time or sequentially, each wavelength of light may heat aspecific material on the substrate more than it heats others. Therefore,as material is removed from the substrate, the wavelength of the lightthat is delivered to the substrate may be changed. For example, after aportion of a material on the substrate is removed, a different materialformed under the material may be removed using the chemical etching incombination with the electron beam and the light beam, but withdifferent parameters for at least the light beam. In this manner,removing a portion of more than one material on a substrate may includedifferentially heating each material with the light beam. In a similarway, when more than one material is being removed from a substrate,parameters of the etch chemistry and/or the electron beam may be changedwhen different materials are being removed. In this manner, parametersof each component used in the de-layering process may be optimized forremoval of the material(s) on the substrate. In addition, parameters ofeach component used in the de-layering process may be altered tomaximize the selectivity of the de-layering process. In particular, theparameters may be altered depending on the composition of the defect,the composition of the material, and in some instances the compositionof the substrate. Preferably, the parameters of the etch chemistry, theelectron beam, and the light beam used in the de-layering process areoptimized to minimize removal of the defect while maximizing removal ofthe material.

As described further above, light beam 122 preferentially heats material116 on substrate 114. Heating material 116 with light beam 122 in thepresence of etch chemistry 124 and electron beam 120 increases thepreferential etching of the horizontal surfaces of material 116. Inparticular, by delivering light beam 122 to substrate 114 coaxially withelectron beam 120, horizontal surfaces of the material can be heatedwithout substantially heating vertical surfaces of the material. In thismanner, electron and light beam assisted chemical etching can besubstantially anisotropic. As a result, the de-layering methodsdescribed herein provide the ability to remove device films whilemaintaining the original aspect ratio of the device features or anyother three-dimensional features on the substrate, which is critical indefect review and analysis.

As shown in FIG. 17, chemical etching in combination with electron beam120 and light beam 122 removes portion 126 of material 116 proximate todefect 112. As further shown in FIG. 17, the remaining portion of thematerial proximate to the defect has upper surface 128 that isapproximately commensurate with a tower surface of detect 112. However,in other embodiments, the portion of the material proximate the defectmay be “over-removed” or “over-etched” such that upper surface 128 islower than a lowermost surface of defect 112. The depth to which thematerial is removed may vary depending on, for example, the analysisthat is to be performed on the defect.

As described further above, portion 126 of material 116 that is removedproximate defect 112 laterally surrounds defect 112. In this manner, theportion of the material that is removed has an area in which the defectresides. As such, all sides of the defect may be exposed after theportion of the material is removed such that analysis of the defect maybe performed from various angles. In one embodiment, the portion of thematerial that is removed has an area that is equal to or less than about10 μm by about 10 μm. Therefore, the area on the substrate in whichmaterial is removed is relatively small, particularly when compared tothe amount of material that is typically removed by other de-layeringprocesses. In this manner, the methods described herein may be performedon product wafers since in most instances removing material from such asmall area on the product wafer should not adversely affect the productwafer as a whole.

The area of the portion of the material that is removed may varydepending on, for example, the area on the substrate that is illuminatedby the electron beam and the light beam. For example, in the methods andsystems described herein, etching takes place only in the presence ofetchant gases in combination with the electron beam. In this manner, thediameter of the electron beam may be altered depending on, for example,the lateral dimensions of the defect, the area that is selected forremoval, the analysis that is to be carried out on the defect, thecharacteristics of the material being removed, and/or thecharacteristics of the substrate. In addition, the area of the portionof the material that is removed may also vary depending on, for example,the area on the substrate that is illuminated by the light beam. Thearea on the substrate that is illuminated by the light beam may bealtered using any method or device known in the art. In one particularexample, the area of the material that is removed is preferably kept ata minimum (to avoid damaging or destroying neighboring structures ifpresent) while allowing enough space around the defect for analysis tobe successfully completed.

The method may also include analyzing defect 112 to determine acharacteristic of the defect. The characteristic of the defect that isdetermined may include any characteristic that may be of interest suchas dimensions (width and height), profile, composition, roughness, etc.Therefore, the characteristic of the defect that is to be determined maydetermine what analysis is performed on the defect. In one embodiment,analyzing the defect may be performed using an electron beam todetermine the characteristic of the defect. In one particularembodiment, as shown in FIG. 17, electron beam 120 that was used forremoval may also be used to analyze defect 112. Parameters of theelectron beam used for removal may be different than parameters of theelectron beam that are used to analyze the defect.

In one such embodiment, electron beam 120 may be used to image thedefect using a technique such as scanning electron microscopy. The imageof the defect may then be used for defect review or to determinecharacteristics such as lateral dimensions of the defect. In anotherembodiment, electron beam 120 may be used to image the defect as thematerial is being removed. In this manner, the defect and thede-layering process can be monitored and recorded, which may providefurther information about the defect, the material proximate the defect,and the de-layering process. The information may be used to monitorand/or control the de-layering process as described further herein. Inanother embodiment, the electron beam may be used to determine acomposition of the defect using a technique such as EDX or AES, asdescribed further above. Once the defect composition has beendetermined, the de-layering methods described herein may be altered tomaximize the selectivity between the defect and the surrounding films.

In another embodiment, an x-ray analysis system (not shown) may be usedto determine a characteristic of the defect. For example, acharacteristic of a defect such as composition can be determined using atechnique such as XPS or XRF. In another example, an XRR technique maybe used to measure a characteristic of a defect such as a concentrationof an element in the defect. The x-ray analysis system may be furtherconfigured as described above. In other embodiments, analysis of thedefect may be performed using any other analytical technique known inthe art. For example, the defect may be analyzed using SIMS, asdescribed further above.

In other embodiments, light beam 122 may be used to analyze the defect.For example, light beam 122 may be used to image the defect. The imageof the defect may then be used to determine one or more characteristicsof the defect. The characteristic(s) of the defect that can bedetermined in this manner may include, but are not limited to, a lateraldimension of the defect, a height of the defect, etc. Parameters of thelight beam may be changed between removal and analysis. For example, awavelength and/or a polarization of the light beam may be changed afterde-layering but before analysis of the defect is performed. Otherparameters of light beam 122 may be similarly altered between removaland analysis. In another embodiment, light beam 122 may be used to imagethe defect as the material is being removed. In this manner, the defectand the de-layering process can be monitored and recorded, which mayprovide further information about the defect, the material proximate thedefect, and the de-layering process. This information can be used tomonitor and/or control the de-layering process as described furtherherein. In other embodiments, a different light beam may be used toanalyze the defect as described herein. This light beam may or may notbe coaxial with electron beam 120.

FIG. 18 illustrates one example of a system that is configured toprepare a substrate for analysis. In this example, the system includeselectron delivery subsystem 130. Electron delivery subsystem 130 isconfigured as an electron column. The electron delivery subsystem isconfigured to deliver electron beam 132 to substrate 134. As shown inFIG. 18, the system is also configured to deliver light beam 136 tosubstrate 134. Light beam 136 and electron beam 132 are delivered toapproximately the same spot on substrate 134.

As shown in FIG. 18, light beam 136 is delivered to the substrate byfocusing the beam at a glancing angle that is tangential to the outsideedge of objective lens 138 of the electron delivery subsystem. In thismanner, the light beam is off-axis with respect to the electron beam. Inother words, the light beam is not delivered to the substrate coaxiallywith the electron beam. This configuration allows the light beam to befocused on the substrate without any modifications to the electroncolumn. However, because the light beam is focused at a glancing angle(about 55° from the vertical), the intersection point of the electronbeam focus, the light beam focus and the substrate is criticallydependent on the striking distance the separation of the objective lensand the substrate). Any change in the working distance would cause thelaser beam to overshoot or undershoot the axial point, necessitating are-alignment of the light beam. In addition, as shown in FIG. 19,because light beam 136 lands on substrate 134 at a glancing angle, focalspot 140 of light beam 136 is an ellipse smeared out in the majordiameter by a factor of about 1.74, while focal spot 142 of electronbeam 132 is circular. Also, reflectance 144 of the surface at theglancing angle decreases the amount of energy delivered to the processby the light beam.

Delivering the light beam to the substrate coaxially with the electronbeam eliminates the problems outlined above. As shown in FIG. 19, whenlight beam 146 is delivered to substrate 134 coaxially with electronbeam 132, the focal spots of both beams are circular. In addition, thefocal spot of light beam 146 will be substantially uniform. Therefore,the electron beam focus, the light beam focus, and the substrate willnot be critically dependent on the separation of the objective lens andthe substrate. In this manner, alignment of the light beam is notcritically dependent on the working distance. As such, changes in theworking distance will not require re-alignment of light beam 146.Therefore, the systems described further herein will be easier tooperate than non-coaxial systems. Furthermore, delivering light beam 146to substrate 134 at a substantially normal angle will reduce reflectanceof the light beam from the surface of the substrate. Consequently, thesystems described further herein will have improved delivery of lightenergy to the de-layering process.

FIGS. 20 and 21 illustrate one embodiment of an electron and lightdelivery subsystem that may be included in a system configured toprepare a substrate for analysis. The electron and light deliverysubsystem is configured to illuminate the field of view of an electronbeam with light or laser energy focused to a relatively small spotdiameter. Therefore, the system is configured to enhance the de-layeringprocess by heating the portion of the material that is being removed andto differentially etch different materials. As shown in FIG. 20, theelectron and light delivery subsystem includes light source 148. Lightsource 148 is configured to generate light beam 150. Light beam 150 isdirected by optical component 152 to optical window 154 in column base156 of an electron column of the electron and light delivery subsystem.The optical window may be configured as a vacuum window. The opticalwindow is configured to allow light beam 150 to enter the electroncolumn.

As shown in FIG. 21, electron column 158 is configured to deliverelectron beam 160 to a substrate (not shown). After entering electroncolumn 158 through optical window 154, light beam 150 is focused to aspot (e.g., by a simple lens (not shown)), and this image is focused bylens 162 to mirror 164 and eventually to the substrate. Lens 162 may bea long focal length transfer lens or any other appropriate lens known inthe art. Light beam 150 is reflected from mirror 164. Mirror 164 may bea 45″ metallic mirror. Mirror 164 may also be a convolving laser mirror.Mirror 164 has an aperture (not shown) formed through the mirror.Preferably, the aperture is configured to allow electron beam 160 topass through the aperture. For example, the aperture may be centered inthe mirror and may have a diameter of about 1 mm. In addition, themirror is preferably placed axially in the electron column with theaperture lined up with the axis of electron beam 160. In this manner,the electron beam can follow its axial path through the electron columnand through the aperture in mirror 164. Therefore, after being reflectedfrom mirror 164, tight beam 150 will be coaxial with electron beam 160.In this manner, the electron and light delivery subsystem is configuredto deliver electron beam 160 to the substrate coaxially with light beam150. Although there will be a slight loss of light beam power (e.g.,about 5%) due to the aperture in the center of the mirror, such a lossis acceptable and will not diminish the functionality of the electronand tight delivery subsystem.

The electron and light delivery subsystem shown in FIGS. 20 and 21 maybe included in a system along with a chemical delivery subsystem (notshown) that is configured to delivery one or more chemicals to asubstrate. The chemical delivery subsystem may be configured asdescribed above. The one or more chemicals in combination with electronbeam 160 and light beam 150 remove a portion of a material on thesubstrate proximate to a defect, as shown in FIGS. 16 and 17. Asdescribed above, the defect may be a subsurface defect or a partiallysubsurface defect. In addition, the defect may be a surface defect. Theportion of the material that is removed may have an area that is equalto or less than about 10 μm by about 10 μm, as described above. Asfurther described above, the area of the portion of the material that isremoved may vary depending on, for example, parameters of the electronbeam as well as parameters of the light beam. In some embodiments, thematerial may include a device film. In such an embodiment, the one ormore chemicals in combination with electron beam 160 and light beam 150do not substantially alter an aspect ratio of device features on thesubstrate as further described above.

Light source 148 may be a laser. However, the light source may be anyother appropriate tight source known in the art. In general, lightsources that are relatively bright at their operating wavelengths may beparticularly suitable for use in the systems described herein. Oneexample of an appropriate laser is a Q-switched laser in the 100 mWrange. Another appropriate laser may be a Ti-sapphire laser. The lightsource may also be a single wavelength laser or a multiple wavelengthlaser. In addition, the light beam may be generated using more than onetight source. For example, light from several lasers may be combinedinto an optical train with a combiner. In another example, differentlight beams may be generated by different lasers, and the light beamthat is delivered to the substrate may vary depending on the materialbeing removed. In this manner, not all of the different light beams maybe delivered to the substrate at the same time.

The wavelength of light beam 150 will vary depending on the materialthat is being removed. For example, depending on the material beingremoved, the wavelength of light beam 150 is selected such that thelight can be absorbed by the material. In this manner, the electron andlight delivery subsystem may be configured such that light beam 150heats a material on the substrate as described above. In addition, thelight beam may have one wavelength (e.g., monochromatic light),approximately one wavelength (e.g., near monochromatic light), or morethan one wavelength of light (e.g., polychromatic light or broadbandlight). Examples of appropriate wavelengths include, but are not limitedto, about 1054 nm (near infrared), about 527 nm (visible, green), about350 nm (near ultraviolet), and about 266 nm (ultraviolet). In general,appropriate wavelength(s) may include any wavelength(s) from about 266nm to about 1054 nm.

If light having different wavelengths is delivered to the substrate atthe same time or sequentially, each wavelength may heat a specificmaterial more than it heats others. Therefore, as material is removedfrom the substrate, the wavelength of the light that is delivered to thesubstrate may be changed. For example, after a portion of a material onthe substrate is removed, a different material formed under the materialmay be removed using the chemical etching in combination with theelectron beam and the light beam, but with different parameters for atleast the light beam. In this manner, the electron and light deliverysubsystem may be configured such that light beam 150 differentiallyheats each material with the light beam. In a similar way, when morethan one material is being removed from a substrate, parameters of theetch chemistry and/or the electron beam may be changed when differentmaterials are being removed. In this manner, parameters of eachcomponent used in the de-layering process may be optimized for removalof the material(s) on the substrate. In addition, parameters of eachcomponent used in the de-layering process may be altered to maximize theselectivity of the de-layering process. In particular, the parametersmay be altered depending on the composition of the defect, thecomposition of the material, and in some instances the composition ofthe substrate. Preferably, the parameters of the etch chemistry, theelectron beam, and the light beam used in the de-layering process areoptimized to minimize removal of the defect while maximizing removal ofthe material.

As described further above, light beam 150 preferentially heats theportion of the material on the substrate that is being removed. Heatingthe material with light beam 150 in the presence of an etch chemistryand electron beam 160 increases the preferential etching of thehorizontal surfaces of the portion of the material being removed. Inparticular, by delivering light beam 150 to a substrate coaxially withelectron beam 160, the electron and light delivery subsystem may beconfigured such that light beam 150 heats a horizontal surface of thematerial and does not substantially heat a vertical surface of thematerial. In this manner, electron and light beam assisted chemicaletching can be substantially anisotropic. As a result, the de-layeringmethods described herein provide the ability to remove device filmswhile maintaining the original aspect ratio of the device features orany other three-dimensional features on the substrate, which is criticalin defect review and analysis.

A system that includes the electron and light delivery subsystem shownin FIGS. 20 and 21 may also include an analysis subsystem (not shown).The analysis subsystem is configured to measure a characteristic of thedefect on the substrate. The characteristic of the defect may includeany of those described herein. The characteristic of the defect beingmeasured may determine what analysis is performed on the defect. Theanalysis subsystem may be configured to perform one of the analysistechniques described herein.

In one embodiment, the electron and light delivery subsystem may beconfigured to measure a characteristic of the defect using electron beam160. In this manner, the electron and light delivery subsystem may beconfigured to function as the analysis subsystem. For example, electronbeam 160 that was used for de-layering may also be used to analyze thedefect. Parameters of the electron beam used for de-layering may bedifferent than parameters of the electron beam that are used to measurethe characteristic of the defect. The parameters of the electron beammay be altered between removal and measurement by altering one or moreparameters of the electron and light delivery subsystem. Theparameter(s) of the electron and light delivery subsystem may be alteredor controlled by a processor (not shown) in some embodiments. Theprocessor may be further configured as described above.

In one embodiment, the electron and light delivery subsystem may beconfigured to image the defect using a technique such as scanningelectron microscopy. The image of the defect may then be used for defectreview or to determine characteristics such as lateral dimensions of thedefect. In another embodiment, the electron and light delivery subsystemmay be used to image the defect as the material is being removed. Inthis manner, the defect and the de-layering process can be monitored andrecorded, which may provide further information about the defect, thematerial proximate the defect, and the de-layering process. Thisinformation may be used to monitor and/or control the de-layeringprocess as described above. In another example, the electron and lightdelivery subsystem may be configured to determine a composition of thedefect using a technique such as EDX, which is described further above.Once the defect composition has been determined, the de-layering methodsdescribed herein may be altered to maximize the selectivity between thedefect and the surrounding films.

In other embodiments, light beam 150 may be used to analyze the defect.In this manner, the electron and light delivery subsystem may beconfigured to analyze the defect using light beam 150 and/or electronbeam 160. In one example, light beam 150 may be used to image thedefect. The image of the defect may then be used to determine one ormore characteristics of the defect such as those described furtherabove. Parameters of the light beam may be changed between removal andanalysis as described above. In another embodiment, light beam 150 maybe used to image the defect as the material is being removed. In thismanner, the defect and the de-layering process can be monitored andrecorded, which may provide further information about the defect, thematerial proximate the defect, and the de-layering process. Thisinformation may also be used as described above. In other embodiments,analysis of the defect may be performed using a different light beam(not shown), which may or may not be coaxial with the electron beam.

In another embodiment, the analysis subsystem may include an x-rayanalysis system such as those described above or any of those known inthe art. In other embodiments, analysis of the defect may be performedusing any other analytical technique known in the art. For example, thedefect may be analyzed using SIMS, as described further above. Theanalysis system may be coupled to the system in any manner. For example,the analysis system and the system may be disposed in one housing,coupled by a common processor, a common substrate handler, a commonpower source, a transmission medium, etc. The embodiment of the electronand light delivery subsystem shown in FIGS. 20 and 21 may be furtherconfigured as described herein.

Further modifications and alternate embodiments of various aspects ofthe invention may be apparent to those skilled in the art in view ofthis description. For example, methods and systems for measuring acharacteristic of a substrate or preparing a substrate for analysis areprovided. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the invention. It is to beunderstood that the forms of the invention shown and described hereinare to be taken as the presently preferred embodiments. Elements andmaterials may be substituted for those illustrated and described herein,parts and processes may be reversed, and certain features of theinvention may be utilized independently, all as would be apparent to oneskilled in the art after having the benefit of this description of theinvention. Changes may be made in the elements described herein withoutdeparting from the spirit and scope of the invention as described in thefollowing claims.

What is claimed is:
 1. A system configured to prepare a substrate foranalysis, comprising: a chemical delivery subsystem configured todeliver one or more chemicals to a substrate; and an electron deliverysubsystem configured to deliver an electron beam to the substrate,wherein the one or more chemicals in combination with the electron beamremove a portion of a material on the substrate proximate to a defect.2. The system of claim 1, wherein the electron delivery subsystem isfurther configured to measure a characteristic of the defect using theelectron beam.
 3. The system of claim 1, further comprising an analysissubsystem configured to measure a characteristic of the defect, whereinthe analysis subsystem comprises an x-ray analysis system.
 4. A systemconfigured to prepare a substrate for analysis, comprising: a chemicaldelivery subsystem configured to deliver one or more chemicals to asubstrate; and an electron and light delivery subsystem configured todeliver an electron beam to the substrate coaxially with a light beam,wherein the one or more chemicals in combination with the electron beamand the light beam remove a portion of a material on the substrateproximate to a defect.
 5. The system of claim 4, wherein the electronand light delivery subsystem comprises a laser configured to generatethe light beam.
 6. The system of claim 4, wherein the electron and lightdelivery subsystem comprises an electron column, and wherein theelectron column comprises an optical window configured to allow thelight beam to enter the electron column.
 7. The system of claim 4,wherein the electron and light delivery subsystem comprises a mirrorwith an aperture formed through the mirror, wherein the electron beampasses through the aperture, and wherein the light beam is reflectedfrom the mirror such that the light beam is coaxial with the electronbeam.
 8. The system of claim 4, wherein the electron and light deliverysubsystem is further configured such that the light beam heats thematerial.
 9. The system of claim 4, wherein the electron and lightdelivery subsystem is further configured such that the light beam heatsa horizontal surface of the material and does not substantially heat avertical surface of the material.
 10. The system of claim 4, wherein theelectron and light delivery subsystem is further configured to measure acharacteristic of the defect using the electron beam.
 11. The system ofclaim 4, further comprising an analysis subsystem configured to measurea characteristic of the defect, wherein the analysis subsystem comprisesan x-ray analysis system.